Unseasonally high temperatures have brought our little vineyard ahead of schedule. Last year we saw our vines starting to bloom just before Mothers Day. This year it's happening about two weeks earlier.Grapes have no internal timer, they just respond to the temperature.The Winkler scale, expressed in growing degree days, was developed in the 1940's by the university of Davis as a method to quantify heat available for vine development during the growing season and identify 5 climate zones for suitable grape varietals.Temecula, with 3,000–3,500 degree days is in Region III, similar to the Rhône in France. Napa and Paso Robles have an average between 2,500–3,000 degree days. They are Region II, similar to Bordeaux.The Winkler Scale is calculated as as the sum of degree days over 10°C (50 °F) from April 1 until October 31.= Σmax [(avg. daily temp. – 10), 0] (ref.: Arnold J. Bloom, Dept. of Plant Sciences, UC Davis)However, if the growing season starts earlier due to climate change, the formal calculation start date of April 1 is out of pace with the actual grape vine growth. It leads to a lower growing degree count till harvest (100-120 days after flowering), as grapes don't care about the date.It's time to reconsider the Winkler calculation method and factor in the actual growing cycle of the grapes.The Winkler method assumes that grapes start growing at average day temperatures higher than 10°C/50 °F. A good adjustment to deal with the new reality of climate change is defining the day where an daily temperature of 10°C/50 °F is reached as the new Winkler growing degree start date. That would make the Winkler scale future proof.

Cost management and water use reduction have been the main reasons why we wanted to automate the irrigation of our vineyard.So far, our vineyard irrigation was done manually. Labour intensive, and probably not the most efficient use of irrigation water.In order to optimize water usage, it is better to irrigate more frequently using shorter times and avoid evaporation by scheduling at night.Our irrigation system uses 2" pipes, and water pressure at our water mains connection is around 120 PSI. We have 2 irrigation blocks of approximately 1500 vines, each vine is served with 2 drippers of 1 gallon/hr. To avoid excessive pressure drop, we irrigate only one block at a time @ 50 gallons/minute.We found that the Hunter Sprinkler ICV201GDC ICV irrigation control valves are very suitable for our purpose. These valves come optionally with a DC latching solenoid (Hunter Sprinkler 458200 DC Latching Solenoid) that can be used in combination with a battery operated controller. That saves trench digging and running wires to operate the irrigation valves with a controller from the house. Added bonus of the Hunter valve is the option of being controlled by a micro controller like the Arduino.

The latching solenoid can easily be controlled with an Arduino board and a low cost motor driver module. We purchased a driver module (L9110S DC Stepper Motor Driver Module H Bridge) on-line for less than $6.The module needs 2 digital control lines (Arduino pin 13: latching on, and pin 12: latching off) per solenoid. The L9110S is a dual motor driver, so 2 valves can be controlled by one single module.The solenoid needs 9V to operate, a small battery provides this to the motor driver module. The solenoid requires only a 10 msec -or longer- pulse to switch state, so the average consumed energy from the battery can be very low. The motor driver board comes with an indicator LED that should be removed to avoid battery drain.Here is a simple Arduino demo sketch:/* Turns on a Hunter DC latching solenoid on for one second, then off for one second, repeatedly. This example code is in the public domain. */